钛合金蜂窝蒙皮脱焊线性调频激励红外检测

变蒙皮厚度的钛合金蜂窝在航空航天领域有着广泛的应用,蒙皮脱焊是钛合金蜂窝结构最常见的缺陷类型之一。传统锁相红外检测由于调制频率单一,不能对变蒙皮厚度的蒙皮脱焊实现一次性检测,检测效率低。针对这一问题,研究了线性调频激励红外检测以及激励参数选择方法。使用ANSYS建立了钛合金蜂窝有限元仿真模型,通过相关算法计算了对应脱焊区域和正常区域的相位差,分析了频带范围、啁啾时间对相位差绝对值最大值的影响以及蒙皮厚度与相位差绝对值最大值所在频率成分的关系。利用线性调频激励对预制脱焊缺陷的蜂窝试样进行了实验研究,获得了不同频带范围和不同啁啾时间下的相位图。实验结果表明,采用频带范围为0.01~0.21 Hz,啁啾时间为22 s的线性调频信号可以对蒙皮厚度为0.6~1.2 mm的钛合金蜂窝实现一次性检测,为钛合金蜂窝结构的实际检测提供了工艺指导。

Detection of skin desoldering defect in Ti-alloy honeycomb using linear frequency modulated infrared imaging

Ti-alloy honeycomb with variable skin thickness has been widely used in the aerospace field.Skin desoldering is one of the most common defects of Ti-alloy honeycomb sandwich.Because of single frequency,traditional lock-in thermography cannot defect desoldering under skin with a variety of thicknesses in one time and has low detection efficiency.To solve this problem,linear frequency modulated infrared imaging and excitation parameter selection method were studied.The finite element simulation model of Ti-alloy honeycomb was established by using ANSYS.Phase difference between desoldering region and normal region was calculated through correlation algorithm and the relationship between freqnency bandwidth,chirp time,skin thickness and maximum of phase difference absolute value was analyzed.Honeycomb sample with prefabricated desoldering defects was experimentally studied using linear frequency modulated exciting.Phase diagrams with different frequency bandwidth and different chirp time are obtained.The results show that one-time detection of Ti-alloy honeycomb with skin thickness 0.6-1.2 mm can be realized using linear frequency modulated signal with the frequency range 0.01-0.21 Hz and chirp time 22 s.These results provide a technical guidance for the practical detection of Ti-alloy honeycomb sandwich structure.